A family member was diagnosed with lung cancer. These are the common symptoms the doctor told me when I asked about them: persistent coughing, typically with blood. Breathlessness, tiredness, swelling of the face and neck area, and fever. all of them can, and are, a lot more commonly caused by things nowhere near as serious however.
If you've been checked out, then I am sure you're fine. Shortness of breath can be caused by a lot of things. It could be tension in your chest due to anxiety or stress, or a sinus issue, or a throat issue. Even something like indigestion can cause horrible breathlessness that persists as long as the issue does.